From: Jeff L Jones (jeff@spoonless.net)
Date: Thu Mar 20 2008 - 21:05:44 MDT
On Thu, Mar 20, 2008 at 7:54 PM, Jeff L Jones <jeff@spoonless.net> wrote:
> In our universe however, which contains dark energy, the situation is
> different. There *is* an event horizon about 16-billion light years
> away. (Note that it's a bit further away than 13-billion lightyears,
> the Hubble horizon, but not as far as the current "radius of the
> visible universe" which is 45-billion lightyears... the distance to
> the furthest objects we can currently see). This event horizon is
> created by the fact that the expansion is accelerating, which traps
> light in a region of size 16-billion lightyears (and this region is
> currently shrinking). So in a sense, we *are* in a black hole.
> Although it's again usually not said that way.
Actually, I think the reason why it's not called a black hole is
because we are *outside* the event horizon (from our perspective at
least). Although the event horizon (sometimes called the deSitter
horizon) does radiate Hawking radiation just like any black hole
would. So it has a temperature and all of the usual properties
associated with black holes. But it's due to the dark energy, not due
to the matter density in our region.
Jeff
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